Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$138.99	11.215%	$154.5777	$154.58	$154.60	$154.60
Purchase #2	$88.83	3.116%	$91.5979	$91.60	$91.60	$91.60
Purchase #3	$66.72	10.556%	$73.763	$73.76	$73.75	$73.80
Purchase #4	$58.48	10.733%	$64.7567	$64.76	$64.75	$64.80
Purchase #5	$228.76	6.154%	$242.8379	$242.84	$242.85	$242.80
Purchase #6	$37.54	13.588%	$42.6409	$42.64	$42.65	$42.60
Purchase #7	$86.36	11.472%	$96.2672	$96.27	$96.25	$96.30
7 purchase totals =	$705.68		$766.4413	$766.45	$766.45	$766.50